Your object is a 3Dsolid which is not in your ssget list.
Try this:
(defun c:CB2 (/ pt1 p1 p2 lay lad copyb)
(setvar "osmode" 35)
(setq lad (getvar "clayer"))
(and
(setq pt1 (getpoint "\nPick Base Point: "))
(setq ent (entsel "\nSelect object for layer filter."))
(setq lay (cdr (assoc 8 (entget (car ent)))))
(setvar "osmode" 0)
(setq p1 (getpoint "\nSelection Set: First corner :"))
(setq p2 (getcorner p1 "\nSecond corner :"))
(setq copyb (ssget "w" p1 p2
(list '(0 . "*polyline,circle,ellipse,region,3dsolid") (cons 8 lay))))
(cadr (sssetfirst nil copyb))
(command "COPYBASE" "_non" pt1 copyb "")
)
(setvar "clayer" lad)
(setvar "osmode" 35)
(princ)
)